Rotary stripper for well pipe strings



Aug. 23, 1966 c. c. BROWN ROTARY STRIPPER FOR WELL PIPE STRINGS Filed Oct. '7, 1963 /C'E/?0 6'. BROWN 6 I NVEN TOR.

ATTORNEY United States Patent 3,268,233 ROTARY STRKPPER FOR WELL PIPE STRINGS Cicero C. Brown, Houston, Tex., assignor to Brown Oil Tools, Inc, Houston, Tex, a corporation of Texas Filed Get. 7, 1963, Ser. No. 314,154 Claims. (Cl. 277-311) This invention relates to well head equipment and particularly to a rotary pipe stripper and seal device.

In the drilling and, frequently in the operations connected with the completion of oil and gas wells, it is necessary to rotate the drilling or other pipe string while the string is being inserted or Withdrawn from a well bore. It is the usual practice to provide a form of seal, usually termed a stripper, in or near the well head to seal about the pipe as it is moved into and out of the well. Ordinarily such strippers are secured to the well head and where rotational movement of the pipe string is involved, they are effective in maintaining a satisfactory seal about a pipe string as it is moved into and out of the well bore. The stripper element will generally be constructed of a resilient rubber or rubber-like composition which will expand and contract as required in order to allow the passage of enlargements on the pipe string, such as collars, through the stripper. Where such a stripper is secured against rotation and it is necessary to rotate the pipe string, excessive wear frequently occurs which destroys the seal formed by the stripper element and may result in blowouts or other serious and hazardous conditions, as well as necessitating frequent replacement of the stripper element, with the consequent delay and expense.

The present invention is directed to a so-called rotarytype stripper, which is adapted to maintain an effective seal about the pipe string as the latter is moved in and out of the well bore accompanied by rotations of the pipe string, and thereby obviates the difficulties encountered with a stationary stripper.

Rotary strippers are, themselves, not new in the well drilling art. However, the present invention has for its principal object the provision of an improved form of rotary stripper which is comparatively simple in design and highly efficient in its sealing function. The stripper, in accordance with this invention, is adapted for use when running and operating pipe strings in a well bore, for example, when snubbing a pipe string into and out of a well bore when the well is under high pressure, when drilling out bridges or other obstacles in a well bore, and the like.

Various other objects and advantages of this invention will become more readily apparent from the following detailed description when read in conjunction with the accompanying drawing which illustrates useful embodiments in accordance with this invention.

FIG. 1 is a longitudinal, quarter-sectional view illustrating a stripper device in accordance with this invention, mounted on a wellhead and in sealing relation to a pipe string being run therethrough;

FIG. 2 is a cross-sectional view taken generally along line 2-2 of FIG. 1; and

FIG. 3 is a view generally similar to FIG. 1 but showing a somewhat modified design.

Referring to the FIGS. 1 and 2, the stripper device, in accordance with this invention, comprises a tubular body or housing having a bore 11 and provided at its lower end with an annular bolt flange 12, by means of which the housing may be secured to the flange 13 of a wellhead fitting P, such as a conventional casinghead. Housing 10 is provided at its upper end with an internally threaded socket 14 having a bottom 15. An internal shoulder 16 is formed on the wall of bore 11 at a point a short distance below socket 14 and provides a seat for rotationally 3,268,233 Patented August 23, 1966 supporting a stripper assembly, designated generally by the numeral 17.

Stripper assembly 17 includes a hanger ring 18 having a diameter somewhat larger than the internal diameter of shoulder 16 and provided with an undercut surface forming a downwardly facing shoulder 19 adapted to seat on shoulder 16. Hanger ring 18 is formed with a reduced external diameter downward extension 20 to which is molded or vulcanized a sealing element 21 constructed of a suitable rubber or rubber-like, flexible resilient composition material. The lower exterior end portion 22 of the sealing element extending below the lower end of extension 20 is of downwardly tapering frusto-conical shape having an axial bore 23 adapted to constrictively seal about a pipe string P which is to be moved in and out of the well through casinghead F, and which may be rotated. The normal diameter of bore 23 of lower portion 22 of the sealing element is made to a nominal dimension somewhat smaller than the external diameter of the pipe string to be run therethrough and its resilience and expansibility permits passage of collars C which connect together the sections of pipe string P. A reinforcing and support collar 24, constructed of metal, is inserted in the bore of seal element 21 above the lower end thereof and comprises a plurality of complementary segments formed by splitting collar 24 longitudinally. These metallic segments are inserted into the inner wall of seal element 21, being vulcanized thereto, and arranged in such way that when the seal element is fully contracted about pipe P, the lower ends of the segments of collar 24 will bear against the pipe wall and form therewith a darn or closure about the pipe to resist extrusion along the pipe of the material comprising the seal element when the stripper is subjected to high pressure from within the well. The upper ends of the segments of collar 24 are provided with inwardly turned lips 25 having rounded peripheral edges which are interengageable with an outwardly turned and rounded annular lip 26 formed on a downward extension 20 of the hanger ring. The interengagement of lips 25 and 26 form a hinge or rocking connection between the reinforcing collar segments and the hanger ring which allows the collar segments to expand and contract with the body of seal element 21 as the latter is expanded and contracted by the passage of enlargements such as collar C through bore 23. The upper portion of hanger ring 18 is counterbored at 28 interiorly thereof to a point a short distance above lip 26 and is adapted to receive an elongate sleeve 29, the bore of which is flush with the bore of hanger ring extension 20. Cooperating threads 30 in the counterbore 28 of the hanger ring and on the exterior of sleeve 29 provide means for threadedly securing sleeve 29 to the hanger ring. By the described arrangement of sleeve 29 with respect to the hanger ring, the sleeve will be concentrically spaced from housing 10 to provide an annular space 31 therebetween. A tubular bushing 32 is adapted to be screwed into socket 14 to close the annular space and is provided with an external seal ring 33 adapted to sealingly engage the wall of socket 14 near its upper end. Bushing 32 is counterbored from its lower end to form a seat 34 for an antifriction bearing 35 which is disposed between seat 34 and the upper end of hanger ring 18, thereby providing a thrust hearing between the stripper assembly and the end of bushing 32. The latter is also counterbored from its upper end at 36 to form a stuffing box in which seal packing 37 is disposed to seal between the exterior of sleeve 29 and bushing 32. An annular gland nut 38 is screwed into the upper end of counterbore 36 of the bushing to compress packing 37. It will be seen that packings 33 and 36 will serve to effectively seal off the annular space between sleeve 29 and housing 10 above bearing 35.

In operation, when pipe string P is rotated, the friction between pipe P and lower portion 22 of the seal element will cause the latter to rotate with the pipe. When no pressure exists, shoulder 19 of the hanger ring will rotate on shoulder 16 of the housing. However, whenever pressure is present in the well, as is usually the case, it will be exerted upwardly against seal element 21 and will not only cause the latter to be compressed more tightly about the exterior of the pipe string, but will cause an upward thrust on the stripper assembly which will be taken on thrust bearing 35, which will permit ready rotation of the stripper assembly, despite the pressure.

FIG. 3 illustrates a modification including changes in the housing to adapt it for connection to a screw-type wellhead fitting and in the bearing structure for rotatably supporting the stripper assembly in the housing.

In this modification, tubular housing a having a bore 11a terminates at its lower end in an internally threaded socket 12a for connection to a screw-type wellhead fitting (not shown) of well known and generally conventional construction. Housing 10a is provided at its upper end with an internally threaded socket 14a having a bottom 15a. A tubular bushing 32a is screwed into socket 14a and provided with an external seal ring 33a to sealingly engage the wall of socket 14a. Bushing 32a is adapted to rotatably support a stripper assembly, designated generally by the numeral 170, in bore 11a.

Stripper assembly 17a dimensioned to rotate freely in bore 11a of the housing, includes a hanger ring, seal element, and metal reinforcing collar, identical with the corresponding elements of FIG. 1 and identified by the same parts numerals. An elongate tubular sleeve 2% is screwed into socket of hanger ring 18 and is radially spaced from bushing 32a. Sleeve 29a is provided with an external enlargement 29b defining upper and lower bearing seats 34a and 34b, respectively. Bushing 32a is counterbored from its upper end to form the internal bearing seat 32b at a point below bearing seat 34b. Bushing 32a is counterbored from its lower end to form the stufling box 36a in which seal packing 37a is disposed to seal between the exterior of sleeve 29a and bushing 32a. A gland ring 38a is screwed into the lower end of counterbore 36a to compress packing 37a. A first anti-friction bearing a is seated between seats 32b and 34b and a second anti-friction bearing 35b is seated on shoulder 34a and held in place by a gland ring 38b screwed into the upper end of bushing 32a. Bearings 35a and 3511 will thus be elfective to take the thrust in either direction between the stripper assembly and the housing. Bearing seat 32b is functionally equivalent to shoulder 16 of the first described embodiment for rotatably supporting the stripper assembly in the housing.

A conventional grease fitting 40 may be installed in the side of housing 10a for introduction of lubricating grease into the annular space between bushing 32a and sleeve 29a about bearings 35a and 35b.

From the foregoing, it will be seen that the specific stripper construction herein above described is a very simple, yet highly efficient, device for maintaining effective sealing about a pipe string which is being moved longitudinally through the assembly, while at the same time, providing for easy rotation of the sealing element, with the result that the stripper element will be subjected to a minimum amount of wear and will, therefore, not require replacement at frequent intervals, even though the operation is conducted under high pressures from the well.

I have found that instead of using the more conventional rubber or rubber-like compositions, such as the artificial rubbers Hycar and Neoprene, and the like, for seal element 21, a more efficient seal element is provided by using a polyurethane elastomer composition, which is found to be not only a more efiicient sealing element, but is less subject to damage by oil and by abrasion dur ing use.

One form of polyurethane elastomer suitable for use in the device herein described is a material of about Durometer hardness.

It will be'understood that changes and alterations may be made in the details of the illustrative embodiments within the scope of the appended claims, but without departing from the spirit of this invention.

What I claim and desire to secure by Letters Patent is:

1. A rotary stripper for well pipe strings, comprising a tubular body attachable to a Wellhead fitting through which a pipe string is moved, internal shoulder means in the bore of the body, a stripper assembly mounted in the bore of said body, means rotatably supporting said assembly on said shoulder, said stripper assembly including a hanger ring, a flexible resilient stripper element pendent from said hanger ring, the exterior of said stripper element being of downwardly tapering frustoconical shape and having an axial bore dimensioned to constrictively sea-l about a pipe string extending therethrough, a metallic reinforcing collar comprising a plurality of complementary segments molded into the bore wall of said stripper element spaced from its lower end, said segments being hingedly secured to said hanger ring for radial movement with the expansion and contraction of said stripper element, an upwardly extending tubular sleeve secured to the hanger ring in concentric spaced relation to said body to define an annular space therebetween, a tubular bushing extending into said annular space and threadedly secured to said body, said rotatable supporting means including antifriction bearing means positioned in said annular space between said bushing and said stripper assembly, and means sealing between said sleeve and said bushing.

2. A rotary stripper according to claim 1 wherein said stripper element is constructed of a polyurethane elastomer having a Durometer hardness of about 80.

3. A rotary stripper for well pipe strings, comprising a tubular body attachable to a wellhead fitting through which a pipe string is moved, internal shoulder means in the bore of the body, a stripper assembly mounted in the bore of said body, means rotatably supporting said assembly on said shoulder, said stripper assembly including a hanger ring, a flexible resilient stripper element pendent from said hanger ring, the exterior of said stripper element being of downwardly tapering frusto-conical shape and having an axial bore dimensioned to constrictively seal about a pipe string extending therethrough, a metallic reinforcing collar comprising a plurality of complementary segments molded into the bore wall of said stripper element spaced from its lower end, said segments being hingedly secured to said hanger ring for radial movement with the expansion and contraction of said stripper element, an upwardly extending tubular sleeve secured to the hanger ring in concentric spaced relation to said body to define an annular space therebetween, said rotatable supporting means including external shoulder means on said sleeve member and antifriction bearing means between said internal and external shoulder means, a tubular bushing extending into said annular space and threadedly secured to said body, and means sealing between said sleeve and said bushing.

4. A rotary stripper for well pipe strings, comprising a tubular body attachable to a wellhead fitting through which a pipe string is moved, internal shoulder means in the bore of the body, a stripper assembly mounted in the bore of said body, said stripper assembly including a hanger ring rotatably seated on said shoulder means, a resilient annular stripper element pendent from said hanger ring, the exterior of the lower end portion of said stripper element being of downwardly tapering frustoconical shape and having an axial bore dimensioned to constrictively seal about a pipe string extending therethrough, a metallic reinforcing collar comprising a plurality of complementary segments molded into the bore wall of said stripper element spaced from its lower end, said segments being hingedly secured to said hanger ring for radial movement with the expansion and contraction of said stripper element, an upwardly extending tubular sleeve secured to the hanger ring in concentric spaced relation to said body to define an annular space therebetween, a tubular bushing extending into said annular space and threadedly secured to said body, anti-fricticn bearing means positioned in said annular space between said bushing and said hanger ring, and means sealing between said sleeve and said bushing above said bearing means.

5. A rotary stripper for well pipe strings, comprising a tubular body attachable to a wellhead fitting through which a pipe string is moved, an internal shoulder means in the bore of the body, a stripper assembly mounted in the bore of said body, said stripper assembly including a hanger ring having a reduced diameter extension defining an external downwardly facing shoulder adapted to be rotatably seated on said internal shoulder means, a resilient annular stripper element secured about said extension and extending below the lower end of the extension, the exterior of the lower end portion of said stripper element being of downwardly tapering frustoconical shape and having an axial bore dimensioned to constrictively seal about a pipe string extending therethrough, a metallic reinforcing collar comprising a plurality of complementary segments molded into the bore secured to said body, a thrust bearing means positioned in said annular space in thrust-taking relation between the inner end of said bushing and the upper end of said hanger ring, and means sealing between said sleeve and said bushing above said thrust bearing means.

References Cited by the Examiner UNITED STATES PATENTS 2,163,813 6/1939 Stone et al 2776 X 2,170,916 8/1939 Schweitzer et a1. 27731 X 2,904,357 9/ 1959 Knox 277-31 3,006,413 110/1961 Brown 166-82 3,052,300 9/1962 Hampton 277-31 X 3,083,973 4/ 1963 Lucky 2773l SAMUEL ROTHBERG, Primary Examiner. 

1. A ROTARY STRIPPER FOR WELL PIPE STRINGS, COMPRISING A TUBULAR BODY ATTACHABLE TO A WELLHEAD FITTING THROUGH WHICH A PIPE STRING IS MOVED, INTERNAL SHOULDER MEANS IN THE BORE OF THE BODY, A STRIPPER ASSEMBLY MOUNTED IN THE BORE OF SAID BODY, MEANS ROTATABLY SUPPORTING SAID ASSEMBLY ON SAID SHOULDER, SAID STRIPPER ASSEMBLY INCLUDING A HANGER RING, A FLEXIBLE RESILIENT STRIPPER ELEMENT PENDENT FROM SAID HANGER RING, THE EXTERIOR OF SAID STRIPPER ELEMENT BEING OF DOWNWARDLY TAPERING FRUSTOCONICAL SHAPE AND HAVING AN AXIAL BORE DIMENSIONED TO CONSTRICTIVELY SEAL ABOUT A PIPE STRING EXTENDING THERETHROUGH, A METALLIC REINFORCING COLLAR COMPRISING A PLURALITY OF COMPLEMENTARY SEGMENTS MOLDED INTO THE BORE WALL OF SAID STRIPPER ELEMENT SPACED FROM ITS LOWER END, SAID SEGMENTS BEING HINGEDLY SECURED TO SAID HANGER RING FOR RADIAL MOVEMENT WITH THE EXPANSION AND CONTRACTION OF SAID STRIPPER ELEMENT, AN UPWARDLY EXTENDING TUBULAR SLEEVE SECURED TO THE HANGER RING IN CONCENTRIC SPACED RELATION TO SAID BODY TO DEFINE AN ANNULAR SPACE THEREBETWEEN, A TUBULAR BUSHING EXTENDING INTO SAID ANNULAR SPACE AND THREADEDLY SECURED TO SAID BODY, SAID ROTATABLE SUPPORTING MEANS INCLUDING ANTIFRICTION BEARING MEANS POSITIONED IN SAID ANNULAR SPACE BETWEEN SAID BUSHING AND SAID STRIPPER ASSEMBLY, AND MEANS SEALING BETWEEN SAID SLEEVE AND SAID BUSHING. 